Kinetics and mechanism of oligomerization of cardanol using acid catalysts

The kinetics and mechanism of oligomerization of cardanol over acid catalysts were studied. GPC results showed the formation of a mixture of oligomers such as dimer, trimer, tetramer, etc. IR spectra of the products of oligomerization showed a decrease in the intensity of the double bond absorption band at 1630 cm^?1 and the disappearance of terminal vinyl bands at 895 cm^?1 and 907 cm^?1. ¹H NMR spectra showed drastic changes in the unsaturated proton resonance signals at 5.5δ with respect to saturated protons at 0.2–2.5δ. The ratio of resonance integrals of unsaturated to saturated protons decreased from 1 : 6.5 to 1 : 20 after oligomerization. GPC studies showed that the rate of formation of the dimer, trimer, tetramer, etc. follow an identical path and that the individual oligomers are formed in the same weight percentage at any time during the reaction. A kinetic scheme is proposed to explain this phenomenon. Kinetic studies showed that the oligomerization reaction follows first order kinetics with respect to the monomer concentration and the rate constant is K = 6.6 × 10^?5s^?1. A probable mechanism for the oligomerization of cardanol is proposed.     

Plasma immersion ion implantation for SOI synthesis: SIMOX and ion-cut

We have demonstrated feasibility to form silicon-on-insulator (SOI) substrates using plasma immersion ion implantation (PIII) for both separation by implantation of oxygen and ion-cut. This high throughput technique can substantially lower the high cost of SOI substrates due to the simpler implanter design as well as ease of maintenance. For separation by plasma implantation of oxygen wafers, secondary ion mass spectrometry analysis and cross-sectional transmission electron micrographs show continuous buried oxide formation under a single-crystal silicon overlayer with sharp Si/SiO₂ interfaces after oxygen plasma implantation and high-temperature (1300°C) annealing. Ion-cut SOI wafer fabrication technique is implemented for the first time using PIII. The hydrogen plasma can be optimized so that only one ion species is dominant in concentration and there are minimal effects by other residual ions on the ion-cut process. The physical mechanism of hydrogen induced silicon surface layer cleavage has been investigated. An ideal gas law model of the microcavity internal pressure combined with a two-dimensional finite element fracture mechanics model is used to approximate the fracture driving force which is sufficient to overcome the silicon fracture resistance.     

Influence of low-frequency electromagnetic fields on living organisms

Recent research reports appear to indicate a real possibility that the low-frequency electromagnetic field produced by the power transmission and distribution network presents a health problem. A critical assessment of the available information is presented here. The state of knowledge, available evidence and conflicting reports indicate a definite need for interim action by the power industry. New direction for analytical research, possible interim avoidance measures, proper advice to clients and the public are discussed. Detailed mathematical modeling for the linear and nonlinear dynamics of DNA and the chromosome as a whole is suggested.     

Study of defect states in a-Se<Subscript>85</Subscript>Te<Subscript>15−<Emphasis Type="Italic">x</Emphasis></Subscript>Pb<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript> thin films by space charge limited conduction mechanism

Current–Voltage (I–V) characteristics have been studied at various temperatures in vacuum evaporated thin films of a-Se₈₅Te_15−x Pb _x (x = 0, 2, 4, 6) alloys. These characteristics show that, at low electric fields, an ohmic behaviour is observed. However, at high electric fields (E ∼ 10⁴ V/cm), the current becomes superohmic. At high fields, in case of samples having 0 and 2 at% of Pb, the experimental data fits well with the theory of space charge limited conduction (SCLC) in case of uniform distribution of localized states in the mobility gap. Such type of behaviour is not observed at higher concentration of Pb in the present glassy system due to high conductivity. In these samples, joule heating due to large currents may prohibit the measurement of SCLC. Using the theory of SCLC for the uniform distribution of the traps, the density of localized defect states near Fermi level is calculated for these compositions. The results indicate that the density of defect states near Fermi level increases on addition of Pb to binary Se₈₅Te₁₅alloy. This is explained in terms of electronegativity of Pb as compared to host elements.     

Experience with Applying Formal Methods to Protocol Specification and System Architecture

In the last three years or so we at Enterprise Platforms Group at Intel Corporation have been applying formal methods to various problems that arose during the process of defining platform architectures for Intel's processor families. In this paper we give an overview of some of the problems we have worked on, the results we have obtained, and the lessons we have learned. The last topic is addressed mainly from the perspective of platform architects.     

Stability analysis of double-diffusive solar ponds with non-constant temperature and salinity gradients

In this communication, the stability of the double-diffusive solar ponds with non-uniform temperature and salinity gradients has been investigated. This is a further generalization of our approach to this problem initiated in Ref. [7]. Using a stochastic approach, the linearized system of basic equations of motion is reduced to a single integro-differential equation. For convective motion, this equation reduces to a time-independent Schrödinger equation for a particle moving in a potential field ƒ(Z) characterized by the non-uniform temperature and salinity gradients. This equation can, in general, be solved (exactly or approximately depending on the form of the gradient profile) by methods commonly used in quantum mechanics.

In the Appendix, we show that, for a quadratic gradient profile, the above equation has an analytical solution similar to that obtained by Zangrando using numerical computations.     

Conductivity study of polyethylene oxide (PEO) complexed with sodium bicarbonate

Ion conducting thin film polymer electrolytes based on polyethylene oxide (PEO) complexed with NaHCO₃ salt has been prepared using solution-cast technique. The complexation of NaHCO₃ salt with PEO is confirmed by XRD and IR studies. DC conductivity in the temperature range 303–368 K has been evaluated. The conductivity is found to increase in the PEO complex with the NaHCO₃ salt and also with an increase in temperature. Using this polymer electrolyte, an electrochemical cell with the configuration Na/(PEO + NaHCO₃)/(I₂ + C + electrolyte) has been fabricated and its discharge characteristics studied. Open Circuit Voltage (OCV) and Short Circuit Current (SCC) are found to be 2.69 V and 1.28 mA, respectively. Other parameters associated with the cell are evaluated and presented in this paper.     

On the improvement of detection characteristics of trans-stilbene crystals by improving crystal perfection

Organic molecular scintillating crystals are noted for their good timing and particle discrimination process. Trans-stilbene is one such candidate noted for its good particle detection characteristics for the past five decades. Progressive strengthening of detection characteristics of trans-stilbene has been attempted by improving crystal perfection. A series of timing resolution studies have been carried out for the Bridgman grown trans-stilbene crystals under different experimental conditions. The results were compared with the previously reported values. Pulse shape discrimination process has been carried out for ²⁴¹Am and ²⁵²Cf sources and good discrimination has been obtained for gamma-alpha and gamma-neutron sources from the grown organic phosphor crystal. Electronic Publication